1. Field of the Invention
This invention relates generally to sports equipment and more particularly to methods and apparatus for stringing a racquet.
2. Description of the Prior Art
Racquets are used in a number of popular games including tennis, badminton, racquetball, and squash. A racquet typically includes an elongated handle, a generally elliptically shaped head attached to one end of the handle, and a network of string stretched across the racquet head.
While there are many ways to string a racquet, by far the most common method is the so called "basket weave". To string a racquet with a basket weave a long segment of string is woven back and forth across the racquet head to form a warp. The string is then woven though the warp in an over and under pattern to form a weft.
Traditional stringing methods are time consuming processes and require trained technicians in their implementation. These factors add to the cost of stringing a racquet.
A problem with the basket weave string pattern for racquets is that the rebound characteristics are not constant across the entire face of the racquet. The so called "sweet spot" where the maximum ball rebound occurs is a relatively small area located near the center of the basket weave string pattern. Areas farther from the center of the string pattern are far less rebound efficient.
Another disadvantage of the basket weave is that the strings are tensioned by pulling on an end portion of the string, causing an uneven tensioning of the string across the face of the racquet. In order to insure a certain minimum tension along the length of the string, portions of the string may be over tensioned, reducing the useful life of the string.
Yet another disadvantage of the basket weave stringing pattern is that the warp and weft string segments saw against each other each time a ball is hit. This again leads to premature wear and breakage of the strings.
Due to the above mentioned disadvantages of the basket weave a number of alternative racquets stringing methods have been devised. Most notable among these are the chain link stringing methods exemplified in British Pat. No. 3,127 of Baden-Powell, U.S. Pat. No. 4,163,553 of Renfro, and U.S. Pat. No. 4,149,722 of Yager.
In 1885, Baden-Powell devised a string pattern made by "looping" a single continuous string through itself in a manner of a knitted fabric. The "knitting" of the string is performed on a board having removable pegs fitted in holes corresponding to the points of intersection of the lines of stringing. After the string has been "knitted" together, it is laced to the head of a racquet.
In the Renfro patent, a tennis racquet head is strung with string sections formed into zig-zag segments having multiple junction points. Renfro's method includes clamping the racquet head to a peg board and weaving the zig-zag pattern directly onto the racquet head. Each of the zig-zag strings is tensioned by pulling on its end.
Yager's patent is directed to a preformed racquet string comprising a loosely woven network of string woven into a substantially oval shaped pre-string. The pre-string is woven in non-parallel rows such that it is radially expansible. The pre-string is stretched from its periphery and then laced or latched to a racquet head. Since the pre-string is not formed in parallel rows, it is not linearly expansible.
While the pre-strings and stringing methods cited above may be an improvement over the basket weave stringing method, some problems remain unsolved. For example, in the Renfro method the strings are still tensioned one at a time by pulling on their ends as they are laced to the racquet head. In the Baden-Powell and Yager patents, pre-strings are laced to the racquet head by applying a radial tensioning force to perimeter of the pre-strings. This results in a racquet face with a higher tension near the perimeter of the pre-strings than near its center.